Background: Considerable debate is taking place over whether patients with basal-cell carcinoma and other skin neoplasms are at increased risk for internal cancer.
Objective: To investigate risk for subsequent cancer in patients with basal-cell carcinoma.
Design: Population-based cohort study.
Setting: Denmark, from 1978 to 1991.
Patients: 37 674 patients followed for a maximum of 14 years after a first diagnosis of basal-cell carcinoma.
Measurements: The occurrence of subsequent cancer was compared with the expected cancer pattern (which was determined on the basis of national incidence data). Standardized incidence ratios (SIRs), ratios of actual to expected number of cases of cancer, yielded estimates of the relative risk.
Results: During 190 945 patient-years of follow-up, 3663 new cases of cancer occurred where only 3245 were expected. As anticipated, malignant melanoma occurred frequently (SIR, 2.64 [95% CI, 2.21 to 3.13]), but patients were also at increased risk for noncutaneous cancer (SIR, 1.19 [CI, 1.13 to 1.24] for men and 1.09 [CI, 1.03 to 1.16] for women). The excess risk for noncutaneous cancer pertained to cancer of the lip (SIR, 2.07), salivary glands (SIR, 2.45), larynx (SIR, 1.41), lung (SIR, 1.40), breast (SIR, 1.13), and kidney (SIR, 1.30) and non-Hodgkin lymphoma (SIR, 1.36). Patients receiving a diagnosis of basal-cell carcinoma before 60 years of age (SIR, 1.26) had a statistically higher risk for developing new cancer (P < 0.01) than did those receiving the diagnosis at 60 years of age or older (SIR, 1.11). This applied to breast cancer (SIR, 1.37 in patients <60 years of age compared with 1.05 in those ≥ 60 years of age), testicular cancer (SIR, 3.52 in patients <60 years of age compared with 0 seen and 1.96 expected in those ≥ 60 years of age), and non-Hodgkin lymphoma (SIR, 2.50 in patients <60 years of age compared with 1.16 in those ≥ 60 years of age).
Conclusion: In addition to having an increased risk for new skin cancer, patients with basal-cell carcinoma have an increased risk for noncutaneous cancer at various sites. Increased risks for testicular cancer, breast cancer, and non-Hodgkin lymphoma should be kept in mind, particularly for patients in whom basal-cell carcinoma is diagnosed when they are at a young age.